refactor: 将客服后端重构为宿主可嵌入模块

- 注入数据库、运行时配置、统一响应、文件存储和平台 AI 能力，补充业务读写工具与客户快捷操作契约。

- 移除模块内重复的组织、客户、工单、标签、技能、旧工作流、MCP 和迁移实现，将身份权限与业务主体交由宿主管理。

- 使用 libSQL 重构向量存储，并完善图片消息、访客身份、排队调度、企业微信和支持聊天页面。

- 统一 HTTP、DTO 与 WebSocket 的 snake_case 协议，补齐模块初始化、业务动作和公共载荷等回归测试。

internal/services/im_message_asset.go

@@ -10,13 +10,28 @@ import (
 )
 
 type imMessageAssetPayload struct {
-	AssetID    string              `json:"assetId"`
-	Provider   enums.AssetProvider `json:"provider,omitempty"`
-	StorageKey string              `json:"storageKey,omitempty"`
-	Filename   string              `json:"filename,omitempty"`
-	FileSize   int64               `json:"fileSize,omitempty"`
-	MimeType   string              `json:"mimeType,omitempty"`
-	URL        string              `json:"url,omitempty"`
+	AssetID    string                  `json:"asset_id,omitempty"`
+	Provider   enums.AssetProvider     `json:"provider,omitempty"`
+	StorageKey string                  `json:"storage_key,omitempty"`
+	Filename   string                  `json:"filename,omitempty"`
+	FileSize   int64                   `json:"file_size,omitempty"`
+	MimeType   string                  `json:"mime_type,omitempty"`
+	URL        string                  `json:"url,omitempty"`
+	Assets     []imMessageAssetPayload `json:"assets,omitempty"`
+}
+
+func (p *imMessageAssetPayload) items() []*imMessageAssetPayload {
+	if p == nil {
+		return nil
+	}
+	if len(p.Assets) == 0 {
+		return []*imMessageAssetPayload{p}
+	}
+	items := make([]*imMessageAssetPayload, 0, len(p.Assets))
+	for index := range p.Assets {
+		items = append(items, &p.Assets[index])
+	}
+	return items
 }
 
 func parseIMMessageAssetPayload(payload string) (*imMessageAssetPayload, error) {
@@ -28,12 +43,18 @@ func parseIMMessageAssetPayload(payload string) (*imMessageAssetPayload, error)
 	if err := json.Unmarshal([]byte(payload), ret); err != nil {
 		return nil, errorsx.InvalidParamI18n("error.e0344")
 	}
-	ret.AssetID = strings.TrimSpace(ret.AssetID)
-	ret.Provider = enums.AssetProvider(strings.TrimSpace(string(ret.Provider)))
-	ret.StorageKey = strings.TrimSpace(ret.StorageKey)
-	if ret.AssetID == "" {
+	items := ret.items()
+	if len(items) == 0 || len(items) > 9 {
 		return nil, errorsx.InvalidParamI18n("error.e0345")
 	}
+	for _, item := range items {
+		item.AssetID = strings.TrimSpace(item.AssetID)
+		item.Provider = enums.AssetProvider(strings.TrimSpace(string(item.Provider)))
+		item.StorageKey = strings.TrimSpace(item.StorageKey)
+		if item.AssetID == "" {
+			return nil, errorsx.InvalidParamI18n("error.e0345")
+		}
+	}
 	return ret, nil
 }
 
@@ -55,15 +76,38 @@ func buildIMMessageAssetPayload(asset *models.Asset) (string, error) {
 	return string(payload), nil
 }
 
+func buildIMMessageAssetBatchPayload(assets []*models.Asset) (string, error) {
+	if len(assets) == 0 || len(assets) > 9 {
+		return "", errorsx.InvalidParamI18n("error.e0342")
+	}
+	payload := imMessageAssetPayload{Assets: make([]imMessageAssetPayload, 0, len(assets))}
+	for _, asset := range assets {
+		if asset == nil {
+			return "", errorsx.InvalidParamI18n("error.e0342")
+		}
+		payload.Assets = append(payload.Assets, imMessageAssetPayload{
+			AssetID: asset.AssetID, Provider: asset.Provider, StorageKey: asset.StorageKey,
+			Filename: asset.Filename, FileSize: asset.FileSize, MimeType: asset.MimeType,
+		})
+	}
+	data, err := json.Marshal(payload)
+	if err != nil {
+		return "", err
+	}
+	return string(data), nil
+}
+
 func buildIMMessageAssetPayloadForResponse(payload string) string {
 	assetPayload, err := parseIMMessageAssetPayload(payload)
 	if err != nil {
 		return strings.TrimSpace(payload)
 	}
-	assetPayload = hydrateIMMessageAssetPayload(assetPayload)
-	if assetPayload.Provider != "" && assetPayload.StorageKey != "" {
-		if provider, err := storage.NewProvider(assetPayload.Provider); err == nil {
-			assetPayload.URL = provider.GetSignedURL(assetPayload.StorageKey)
+	for _, item := range assetPayload.items() {
+		hydrateIMMessageAssetPayload(item)
+		if item.Provider != "" && item.StorageKey != "" {
+			if provider, err := storage.NewProvider(item.Provider); err == nil {
+				item.URL = provider.GetSignedURL(item.StorageKey)
+			}
 		}
 	}
 	data, err := json.Marshal(assetPayload)
@@ -112,5 +156,13 @@ func validateConversationAsset(asset *models.Asset, conversationID int64, messag
 	if asset.Status != enums.AssetStatusSuccess {
 		return errorsx.InvalidParamI18n("error.e0343")
 	}
+	if conversationID <= 0 || asset.ConversationID != conversationID {
+		// Deliberately use the same error as a missing asset so callers cannot
+		// probe whether an asset belongs to another customer's conversation.
+		return errorsx.InvalidParamI18n("error.e0342")
+	}
+	if messageType == enums.IMMessageTypeImage && !isSupportedVisionImageMIME(asset.MimeType) {
+		return errorsx.InvalidParamI18n("error.e0090")
+	}
 	return nil
 }